Modular intramedullary nail

ABSTRACT

An intramedullary nail apparatus comprises a nail having a proximal portion, a middle portion and a distal portion. The proximal portion has a longitudinal slot adapted to receive at least one fixing element and the distal portion has at least one transverse bore. The proximal portion has a longitudinal axial bore. The apparatus further includes a set of inserts, each of which is adapted to be inserted in the longitudinal bore. Each insert has at least one guiding bore, the orientation and position of which is different for each of the inserts. A method of treating fractures utilizing the intramedullary nail apparatus is also disclosed.

BACKGROUND OF THE INVENTION

The present invention refers to a modular intramedullary nail, moreparticularly to a modular femoral intramedullary nail comprising a nailwhich is composed of a proximal portion, a middle portion and a distalportion, said proximal portion having a longitudinal slot and saiddistal portion having at least one transversal bore.

So-called unreamed locking intramedullary nails have been used for thetreatment of fractures of tubular bones for some time now. Lately, theindications of such intramedullary nails have been extended to includeproximal fractures of the femur shaft, these fractures existing in agreat diversity while their treatment is extremely complex. As aconsequence, a great number of intramedullary nails have been developedwhich take into account the different types of fractures. These nailsonly distinguish themselves by the manner in which the proximal fixingscrews are positioned according to the type of fracture. This leads toan expensive storage of a large number of nails and instruments.Furthermore, it is increasingly difficult for the surgeon and the nursesto master a great number of different implant systems in such a mannerthat an optimum treatment of fractures is ensured.

WO-94/13219 describes an unreamed intramedullary nail of modularstructure which allows a considerable reduction of the number ofrequired intramedullary nails by its diversity in use. Theintramedullary nail is provided with a cylindrical sleeve which isadapted to be slid over its proximal end in a telescopic manner andwhose design allows different modes of attachment in order to adapt theintramedullary nail to the required application. However, such atelescopic attachment is not optimal with respect to biomechanicalaspects, which must be considered as essential on account of the greatloads at the proximal femur, and furthermore, the proximal portion ofthe nail is additionally thickened by the attached sleeve, thusresulting in negative effects with respect to the vascularization of theneck area of the femur head. Finally, the telescopic attachmentcompulsorily lengthens the nail, resulting in a modification of itsoriginal length.

DE 85 33 134 U describes a device for treating a bone fracture, whichcomprises a proximal hollow portion accepting a threaded bolt for fixinga screw in a transversal slot. This device is designed for a particulartype of fracture and does not permit the reduction of requiredintramedullary nails.

SUMMARY OF THE INVENTION

On the background of this prior art, it is the object of the presentinvention to provide a modular intramedullary nail and a relating methodwhere the above-mentioned drawbacks are eliminated and which has anincreased biomechanical stability and ensures a better vascularization.This object is attained by an intramedullary nail wherein the proximalportion comprises a longitudinal bore extending over the longitudinalextension of said slot in the distal direction and an insert which isintended to be inserted in said longitudinal bore, said insertcomprising at least one guiding bore which is intended to receive fixingelements.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail hereinafter with reference todrawings of several embodiments of the invention.

FIG. 1 shows an assembly of the different elements of the intramedullarynail in a partly sectioned view according to a first embodiment of theinvention;

FIG. 2 shows a cross-section according to II—II in FIG. 1;

FIG. 3 shows a cross-section according to III—III in FIG. 1;

FIG. 4 shows an enlarged detail of the distal nail end according to FIG.1;

FIG. 5 shows the intramedullary nail for treating fractures in thecentral area of the shaft according to a second embodiment of theinvention;

FIG. 6 shows the intramedullary nail for treating fractures in thecentral area of the shaft with means of a compression screw according toa third embodiment of the invention;

FIG. 7 shows the intramedullary nail for treating proximal femurfractures with means of a retrograde respectively an antegrade fixationaccording to a fourth embodiment of the invention;

FIG. 8 shows the intramedullary nail for treating proximal femurfractures with means of a retrograde respectively an antegrade fixationaccording to a fifth embodiment of the invention;

FIG. 9 shows the intramedullary nail for treating fractures in thecentral area of the shaft according to a sixth embodiment of theinvention; and

FIG. 10 shows the intramedullary nail for treating fractures in thecentral area of the shaft with means of a compression screw according toa seventh embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Nail 1 is essentially in the form of a cylindrical bar and may bedivided into a proximal portion 2, a middle portion 3, and a distalportion 4. The illustrated nail for the femur is adapted to the anatomyof the femur and therefore curved according to a so-calledantecurvation. The distal portion as well as the middle portion are sodimensioned that the nail can be introduced into the intramedullarychannel without drilling by means of a guiding wire. Within otherembodiments cannulated nails can be used.

Proximal portion 2 is cylindrical and is provided with- a longitudinalbore 5 comprising a partial internal thread 6 whose core diameter isslightly greater than the diameter of longitudinal bore 5. Bore 5 servesto receive an insert 7 whose function will be explained later on. Theproximal end 11 of the proximal portion comprises two guide grooves 12which serve for the rotationally fixed guidance of the non-representeddriving bow on which, according to the indication, the correspondingaiming appliance is fastened in an angularly stable manner. Therefore,at this end of longitudinal bore 5, the internal thread is omitted inorder to prevent gripping between the grooves and the fastening screw ofthe aiming appliance.

Proximal portion 2 is further provided with a throughgoing slot 8 whichextends in parallel to the longitudinal axis. A guiding pin 9, whichserves for a rotationally fixed positioning of insert 7, is disposedinside longitudinal bore 5 and transversally thereto. Underneathlongitudinal bore 5, which extends beyond the longitudinal extension ofslot 8 in the distal direction, the proximal portion is provided with atransversal bore at its distal end.

Middle portion 3 and distal portion 4 of the nail have a smallerdiameter than the cylindrical proximal portion 2. Cross-sections II—IIand III—III show that the middle portion is provided at its proximal endwith a wire groove 13 intended to receive a guiding wire, the wiregroove extending from the distal portion to the proximal side and beinginclined with respect to the longitudinal axis of the nail. As aconsequence, wire groove 13 exits from the nail below proximal portion4, as appears in FIGS. 3 and 4, while assuming the shape of a wirechannel 13A.

Bottom 14 of the groove (see FIG. 2) is rounded in order to provide anoptimum guidance of the guiding wire and to prevent possible notchtensions in the bottom of the wire groove. This kind of guidance allowsa safe and controlled introduction of the nail by means of the guidingwire while preventing, -in contrast to a cannulation, the formation of anon-vascularized clearance.

As already mentioned above, wire groove 13 and wire channel 13A to areprovided on distal portion 4, which means that the design of the guidingmeans for the guiding wire allows a nail which need not be entirelycannulated while the cross-section of the nail, which is smaller due tothe wire groove, reduces the risk of a fat embolism in the course of theintroduction of the nail.

However, in order to carry out the invention, it is not absolutelynecessary to provide the middle and the distal portions with a wiregroove and a wire channel. A central cannulation of the intramedullarynail is also possible.

The lower section of the distal portion is provided with transversalbores 15. Point 16 of the nail is parabolical in order to be passed overthe line of fracture without a great resistance. Transversal bores 15,of which preferably at least two are provided, serve to receive thedistal fixing screws 17. As the case may be, a non-representedlongitudinal slot may additionally be provided on distal portion 4.

For the treatment of fractures in the central area of the shaft, theintramedullary nail according to FIGS. 5 and 6 may be used where theaxial and torsional forces are absorbed by fixing screw 18 intransversal hole 10 as well as by a second fixing screw 18 in slot 8which receives torsional forces exclusively. Instead of fixing screws18, fixing bolts 19 (see FIGS. 7 and 8) may be used which are providedwith hexagon sockets 20. These fixing screws 18 and fixing bolts 19constitute the fixing elements 18 and 19.

Longitudinal bore 5 is protected against an accretion of tissue into thethreaded portion, which would impair the attachment of the explantationinstrument, by means of a cap screw 21. Cap screw 21 is externallythreaded and comprises a hexagonal socket 23 which allows to fasten thescrew.

In the treatment of a fracture of the central shaft area, an activecompression fixation can be effected by means of a compression screw 24(see FIGS. 6 or 10). For this purpose, fixing screw 18 is introducedinto longitudinal slot 8 transversally to the longitudinal axis of thenail by means of the proximal aiming appliance (not shown).Subsequently, compression screw 24 is entered in proximal thread 6 ofthe proximal portion until it contacts fixing screw 18 by its distal end25. As the compression screw is now further entered, the proximalfragment of the bone is displaced relative to the nail until thefracture is closed and an interfragmentary compression is obtained.Compression screw 24 further comprises a shaft portion 26 which isfollowed by an externally threaded portion 27 of greater diameter, aswell as a hexagon socket 28.

As an essential extension of the field of applications of theintramedullary nail according to the invention, more particularly for anantegrade or a retrograde fixation, an insert 7 is provided which mayeither be hollow or solid in design. Insert 7 according to theembodiment shown in FIG. 1 and 5 comprises a through-going longitudinalbore 34 and two guiding bores 29 which are inclined with respect to thelongitudinal axis, more than two guiding bores being possible, but atleast one such bore being provided. In this case, the external diameterof cap screw 21 approximately corresponds to the external diameter ofinsert 7, thus allowing its fastening. A subsequent displacement of theinsert in the longitudinal bore is thus prevented, i.e. a preciselydefined positioning of the insert with respect to the longitudinal axisis ensured. Furthermore, the clamping action excludes any microscopicmovements between the inner wall of the bore and the insert which mightresult in an undesirable abrasion. Finally, the insert increases thebiomechanical stability of the nail by a bracing effect.

Guiding bores 29, which are inclined with respect to the longitudinalaxis, may have different diameters and serve to receive fixing screws 18or fixing bolts 19. The insert further comprises a guiding groove 30 inwhich guiding pin 9 engages and thus ensures a correct introduction ofthe insert in such a manner that guiding bores 29 for the fixing screwsare aligned with respect to slot 8 of the nail. In order to facilitatethe insertion, the guiding groove is enlarged in the manner of a funnelat both its ends. For a retrograde fixation of the fracture, guidingbores 29 a preferably aligned at an angle of 120° to 150° with respectto the longitudinal axis, while they are preferably aligned at an angleof 125° to 150° with respect to the longitudinal axis in the case of anantegrade fixation.

Guiding pin 9 engaging guiding groove 30 can be replaced by otherelements for preventing a misalignment of insert 7. These elements canespecially be integrated into the implantation instrument.

FIG. 7 shows the retrograde respectively antegrade fixation of afracture by means of an insert 31 for a intramedullary nail according toa fourth embodiment comprising a single guiding bore 29 but which isotherwise identical to insert 7. In this FIG. 7 as well as in FIG. 8, itis visible how guiding pin 9 engages in guiding groove 30 of the insertand thus precisely aligns the insert with respect to longitudinal slot8. It further appears that, an insertion of the sleeve with one of itsends 32 facing in the distal direction or with the other end 33 facingin the distal direction allows either a retrograde or an antegradefixation. In this case, as in the case according to FIG. 8, the capscrew 21 serves to fasten the insert by a clamping action andfurthermore as a protection against an accretion of tissue into thethreaded portion.

FIG. 8 shows the use of insert 7 for a intramedullary nail according toa fifth embodiment with two guiding bores 29 in the case of a retrograderespectively an antegrade fixation of the fracture. The considerationswith regard to insert 31 according to FIG. 7 apply in an analogousmanner.

FIG. 9 shows a intramedullary nail for treating fractures in the centralarea of the shaft according to a sixth embodiment of the invention. Thenail is cannulated and comprises a throughgoing slot 45 which extends inparallel to the longitudinal axis. Underneath longitudinal bore 5 whichextends beyond the longitudinal extension of slot 8 in the distaldirection, the proximal portion does not contain a transversal bore atits distal end. Insert 7 comprises at least one guiding bore 29. In theembodiment shown insert 7 comprises two guiding bores 29 which areoriented transversal to the longitudinal axis 46 of insert 7respectively proximal portion 2. Fixing screws 18 are received withinsaid guiding bores 29 whereby another screw is provided in the distalportion 4 to stabilise a fracture of the central area of the shaft.

FIG. 10 shows a intramedullary nail for treating fractures in thecentral area of the shaft according to a seventh embodiment of theinvention using a compression screw 24 to effect an active compressionfixation. First of all insert 7 comprising a longitudinal guiding slot39 is introduced and fixed by means of the cap screw 21. Then, thefixing screw 18 is pushed through the longitudinal guiding slots 39 and8 in a direction transversal to the longitudinal axis 46 of the nail.The initial position of the fixing screw is marked with numeral 18′.Finally, the compression screw 24 is inserted into the internal thread 6of the proximal portion until contacting the fixing screw 18′ in theposition 24′. The shaft of the compression screw 24 transverses thehollow cap screw 21. As the compression screw 24 is now further entered,the proximal fragment of the bone is displaced relative to the nailuntil the fracture is closed and an interfragmentary compression isobtained. The distal end 25 of the compression screw 24 touches thefixing screw 18 in the position shown in unbroken lines.

The intramedullary nail shown and described is to be used for femurfractures. It is clear that the nail can also be provided for treatmentof other fractures, e.g. fractures of the tibia or the humerus. Thebasic advantage of the modular system of this intramedullary nail usinginserts which do not enlarge the space used for the nail is maintained.

It follows from the preceding description that a nail 1 as well as alimited number of inserts allow to treat all kinds of femur, tibia andhumerus shaft fractures as well as the most different proximal femur,tibia or humerus fractures. Besides, the shape of the inserts and thusalso of the longitudinal bore 5 receiving the insert is independent fromthe diameter or the length of the nail. Furthermore, there is no needfor a left-hand and a right-hand form of the nail, which is an essentialadvantage with respect to the use and the storage of this implant. Thecorresponding left-hand or right-hand embodiment of the nail isdetermined by a mere 180° turn when introducing the insert. It furtherfollows from the description that other embodiments of theintramedullary nail such as reconstruction nails can be used accordingto the inventive idea.

What is claimed is:
 1. An intramedullary nail comprising a nail which iscomposed of a proximal portion, a middle portion and a distal portion,said proximal portion having a longitudinal slot extending throuqh theproximal portion in a direction transverse to the longitudinal axis ofthe proximal portion and being adapted to receive at least one fixingelement extending therethrough and said distal portion having at leastone transversal bore, the proximal portion having a longitudinal axialbore extending over the longitudinal extension of said slot and a set ofinserts each of which is adapted to be inserted in said longitudinalbore, each of said inserts comprising at least one guiding bore toreceive said fixing element, the orientation and the position of saidguiding bore being different for each insert of said set of inserts. 2.The intramedullary nail of claim 1, wherein the alignment of the guidingbores of said inserts are inclined with respect to the longitudinal axisof the proximal portion and wherein said inserts are adapted to beinserted and locked in said longitudinal bore with one end facing thedistal direction for retrograde fixation and with the other end facingthe distal direction for antegrade fixation.
 3. The intramedullary nailof claim 1, wherein the alignment of the guiding bores of each of saidinserts is transverse with respect to the longitudinal axis of theproximal portion.
 4. The intramedullary nail of claim 1, furtherincluding a guiding pin which engages in the longitudinal bore of saidproximal portion, and wherein at least one of said inserts is providedwith a corresponding guiding groove for its correctly positionedinsertion.
 5. The intramedullary nail of claim 1, wherein thelongitudinal bore of said proximal portion is internally threaded andprovided with a cap screw.
 6. The intramedullary nail of claim 1,wherein at least one of said inserts and said nail is hollow.
 7. Theintramedullary nail of claim 1, wherein said fixing element comprises afixing element selected from the group consisting of fixing screws,fixing bolts, and blades.
 8. An intramedullary nail comprising a nail(1) which is composed of a proximal portion, a middle portion and adistal portion, said proximal portion having a longitudinal slot andsaid distal portion having at least one transversal bore, said middleportion and said distal portion of the nail being provided with a wiregroove which ends in a wire channel (13A) at the distal end.
 9. Theintramedullary nail of claim 8, wherein the bottom of said wire grooveis rounded.
 10. A method of treating fractures comprising the steps of:(a) placing a nail in the intramedullary space of a bone, the nailhaving a longitudinal axis and a proximal portion, a middle portion anda distal portion, the proximal portion having a longitudinal slot andthe distal portion having at least one transverse bore, whereby theproximal portion includes a longitudinal bore extending over thelongitudinal extension of the slot in the distal direction; (b)introducing at least one distal fixing screw in the at least onetransverse bore; (c) selecting an insert from a set of inserts, each ofsaid inserts having at least one guiding bore, the orientation andposition of the guiding bore being different for each insert of the setof inserts; (d) introducing the selected insert in said longitudinalbore, the insert having at least one guiding bore; and (e) driving onefixing element in the at least one guiding bore of the insert andthrough the longitudinal slot of the nail.